1. Field of the Invention
This disclosure relates generally to photocatalysts and, more particularly, to a method and system for decreasing deactivation in photocatalysts.
2. Description of the Related Art
Ultraviolet (UV) Photocatalytic Oxidation may be used for fluid purification, in particular, indoor air purification. Generally, the irradiation from UV lamps is projected onto a photocatalyst coated substrate in order to purify air by UV Photocatalytic Oxidation. The substrate may be any surface, such as, a flat plate, mesh, or honeycomb. The photocatalyst may be, for example, titanium dioxide (TiO2), which is a common white pigment used in paint that is readily available and economical. UV light is projected on the catalyst promoting the formation of reactive species on the catalyst surface. The reactive species interact with volatile organic compounds in air passing over and absorbing onto the surface of the catalyst to transform the volatile organic compounds into byproducts such as carbon dioxide (CO2) and water.
Volatile organic compounds (VOCs) are known to be any organic compounds that participate in atmospheric photochemical reactions. The aggregate amount of VOCs in air is typically on the order of 1 part per million by volume. Volatile silicon-containing compound (VSCCs) concentrations are also typically present in air, but are typically two or more orders of magnitude lower. VOCs can originate from many sources, such as industrial emissions, building materials, transportation exhaust, paints, cleaning chemicals and building materials. VSCCs arise primarily from the use of certain personal care products, such as deodorants, shampoos and the like, or dry cleaning fluids, and from the use of RTV silicone caulks, adhesives, lubricants and the like. Where VOCs are constructed of carbon-based molecules such as aldehydes, ketones, or hydrocarbon functionalities, VSCCs are typically comprised of silicon oxygen backbone chains that incorporate hydrocarbon pendant groups along the silicon oxygen backbone.
Over the last decade, levels of VSCCs, including siloxanes, in the air have been increasing. Siloxanes are included in health, beauty and personal care products, such as, deodorant, skin cream, hair spray, etc. UV Photocatalytic Oxidation is effective in transforming siloxanes into harmless by-products. Unfortunately, the prior art photocatalysts may become ineffective in a short amount of time, due to conversion of silicon containing compounds to various forms of silica at the surface of the photocatalyst, which block the catalyst active sites.